Importance of Strongly Bound Excited States in the Electronic Spectrum of Be+2

Abstract

Theoretical radiative data are presented for selected transitions involving the strongly bound 12Πu and 14Σ−g states of Be+2. The wavefunctions stem from a Multi-Reference Configuration Interaction (MRD-CI) treatment correlating three valence electrons. Absorption from 12Πu (σ2gπu into 12Δg and 12Σ−g (both σgπ2u) have oscillator strengths ƒ00 of 0.028 and 0.073, respectively. The unusual stability of states having single or double excitation into the πu MO dominates the spectrum and make experimental detection of Be+2 feasible. An absorption ƒ00 of 0.049 for the Rydberg transition 22Δg ← 12Πu(πu → 3dδ) also indicates a high intensity spectrum. Absorption from 14Σ−g generally leads to rupture of the BeBe bond since the upper states are either repulsive 14Πu, 14Σ−u) or metastable (34Πu).